In furnaces of the walking beam conveyor type for heating steel materials such as slabs and billets, skid buttons arranged on skid beams serving as movable beams and fixed beams are repeatedly loaded with the steel material (the material to be heated) at a high temperature, so that heat-resistant alloys, sintered ceramic materials or composite materials of alloy and ceramic are conventionally used for making the skid buttons.
However, use of these materials involves problems. The heat-resistant alloy is not fully satisfactory in high-temperature strength, while the sintered ceramic material is brittle and low in toughness. The alloy-ceramic composite material undergoes degradation due to a reaction between the two component materials when used in a high-temperature environment. To overcome the problems, the present applicant has already proposed a sintered body of Fe-Cr alloy particles and a sintered body of Fe-Cr alloy particles and a particulate oxide of rare-earth element (Unexamined Japanese Patent Publications HEI 2-258946, HEI 2-258947, etc.). These bodies are prepared from an alloy powder or a mixture of alloy powder and particulate oxide of rare-earth element by a desired sintering process.
These sintered bodies are more excellent in oxidation resistance and high-temperature compressive strength than heat-resistant alloys, sintered ceramic materials and alloy-ceramic composite materials, but still remain to be improved in oxidation resistance and high-temperature compressive strength for use in operations which are conducted generally at higher temperatures of at least 1350.degree. C. in recent years. It is therefore desired to provide materials having still higher oxidation resistance and more excellent high-temperature compressive strength.
We have directed attention to techniques of the so-called mechanical alloying process wherein a metal powder and an oxide powder are mixed together to finely disperse the particulate oxide in the state of a solid phase. The oxide-dispersion-strengthened alloys heretofore prepared by the mechanical alloying process are limited to Fe-based alloys and Ni-based alloys, which nevertheless have a drawback. The former alloys are not fully satisfactory in oxide resistance at high temperatures of not lower than 1350.degree. C., while the latter alloys are insufficient in compressive strength at high temperatures of at least 1350.degree. C. Thus, the materials heretofore present are not excellent in both the characteristics of oxidation resistance and compressive strength.
An object of the present invention is to provide a sintered alloy which has outstanding oxidation resistance and compressive strength at high temperatures of not lower than 1350.degree. C. and which is very suitable for use as a material for skid buttons, and a powder for preparing the sintered alloy.